The Research On The Effect Of Surface Texture On Tribological Behavior Of PTFE Composites

Surface texture technology is an effective method to fabricate micro-texture with certain size,shape and arrangement rules on the frictional counterpart surface,which can capture the wear debris,retain lubricant,eliminate abrasive wear,promote the formation of transfer film and improve the tribological properties of polymer materials.Intensively studying the effects of friction counterpart material surface micro-texture on the friction transfer properties of polymer materials and the formation mechanism of transfer film is of great significance to continuously break the service limit and improve reliability of polymer materials.The aim of this thesis is improving the friction and wear properties of PTFE material.The PTFE material and friction counterpart surface texture are selected as the research object,and experimental test is combined with theoretical analysis to research the friction and wear characteristics of the POB and nano-Si O₂ synergistically modified PTFE composites friction,which slide against the counterpart with micro-textured surface.The main research contents and results are as follows:（1）The friction,wear and friction transfer properties of PTFE composites on frictional counterpart surfaces with different roughness were studied.An evaluation method of transfer film performance was proposed,and the influence mechanism of surface roughness and modified fillers on the friction and wear properties of PTFE and transfer film was revealed.The results show that the modified filler and its content match with the roughness of the counterpart surface.The properly matched friction pair is beneficial to the formation of mechanical interlocking effect between the nanoparticles and the asperities on the counterpart surface,which improves the deposition efficiency of the wear debris,and promotes the formation of thin,uniform and continuous transfer film,thus improving the tribological properties of the materials.（2）The BBD response surface method was firstly introduced into the tribology experiment design and parameter optimization.Typical grooved texture design was studied,and the global scope function relation between the texture parameters and results was regression fitted.The grooved texture parameters and their interactions on the friction and wear performances of PTFE composites was explored.The results show that the friction coefficient of PTFE composites has minimum,and volume wear rate has maximum.There are some correlation between the friction and wear of material.The friction coefficient and volume wear rate is difficult to reach the minimum at the same time on a particular grooved texture surface,so the particular surface texture should be designed according to the actual working condition on the friction coefficient and wear rate.（3）The orthogonal experimental method was used to design the pit textured counterpart surface with 3 factors and 4 levels,and the friction and wear performance of PTFE composites on the pit textured counterpart surface were investigated.The influences of the texture parameters on the friction coefficient and volumetric wear rate were analyzed by the range analysis method and the multi-index matrix analysis method.The pit texture parameters were optimized and the mechanism of friction reduction and wear resistance of the pit texture was explored.The results show that the matrix analysis method of multi-index orthogonal test is suitable for the analysis and optimization of the pit texture and its parameters for tribological properties of PTFE nanocomposites.（4）The nodal friction test method was designed,which overcome the shortcomings that traditional tribology test only has the beginning and the end of the state and cannot monitor the friction process.The friction coefficient,wear volume and the dynamic grow process of transfer film of PTFE composites on the pit textured surface were studied.It is found that the composite exhibits fatigue wear on the textured counterpart surface.The wear process can be divided into three typical stages,i.e.,running-in period,transitional period and stable period.Under the action of contact stress and nano-Si O₂ particles,the friction debris captured by texture adheres to the surface of the pit,forming the bonding point and growth point of the transfer film,forming a network structure of embedded micro lubricant on the counterpart surface,and promoting the formation of uniform and continuous transfer film on the counterpart surface.（5）The finite element model of friction pair was established by ABAQUS finite element simulation software,and the contact stress distribution of PTFE composites and the effect of texture parameters on stress distribution under reciprocating friction condition was studied.It provides a theoretical basis for further explaining the mechanism of surface texture improving the tribological properties of materials.The results show that the pit texture improves the stress concentration of the friction pair.The maximum equivalent contact stress is the smallest on the surface of the“□”texture,and the change of texture density does not change the maximum equivalent contact stress.With the increase of the texture depth,the specimen deformation increases,resulting in the stress concentration in a large area.